[analysis_server] Show correct type for enum.values

Fixes https://github.com/Dart-Code/Dart-Code/issues/4877

Change-Id: Ie9b7f223f71c4c79c141ca69356340ef8b15aceb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/350720
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/src/computer/computer_hover.dart

@@ -62,8 +62,10 @@ class DartUnitHoverComputer {
       // element
       var element = ElementLocator.locate(node);
       if (element != null) {
-        // variable, if synthetic accessor
-        if (element is PropertyAccessorElement) {
+        // use the non-synthetic element to get things like dartdoc from the
+        // underlying field (and resolved type args), except for `enum.values`
+        // because that will resolve to the enum itself.
+        if (_useNonSyntheticElement(element)) {
           element = element.nonSynthetic;
         }
         // description
@@ -255,6 +257,20 @@ class DartUnitHoverComputer {
     return staticType?.getDisplayString(withNullability: true);
   }
 
+  /// Whether to use the non-synthetic element for hover information.
+  ///
+  /// Usually we want this because the non-synthetic element will include the
+  /// users DartDoc and show any type arguments as declared.
+  ///
+  /// For enum.values, nonSynthetic returns the enum itself which causes
+  /// incorrect types to be shown and so we stick with the synthetic getter.
+  bool _useNonSyntheticElement(Element element) {
+    return element is PropertyAccessorElement &&
+        !(element.enclosingElement is EnumElement &&
+            element.name == 'values' &&
+            element.isSynthetic);
+  }
+
   static Documentation? computeDocumentation(
       DartdocDirectiveInfo dartdocInfo, Element elementBeingDocumented,
       {bool includeSummary = false}) {

pkg/analysis_server/test/lsp/hover_test.dart

@@ -152,6 +152,42 @@ class HoverTest extends AbstractLspAnalysisServerTest {
   Future<void> test_dartDocPreference_unset() =>
       assertDocumentation(null, includesSummary: true, includesFull: true);
 
+  Future<void> test_enum_member() async {
+    final content = '''
+enum MyEnum { one }
+
+void f() {
+  MyEnum.[!o^ne!];
+}
+''';
+    final expected = '''
+```dart
+MyEnum one
+```
+Type: `MyEnum`
+
+*package:test/main.dart*''';
+    await assertStringContents(content, equals(expected));
+  }
+
+  Future<void> test_enum_values() async {
+    final content = '''
+enum MyEnum { one }
+
+void f() {
+  MyEnum.[!va^lues!];
+}
+''';
+    final expected = '''
+```dart
+List<MyEnum> get values
+```
+Type: `List<MyEnum>`
+
+*package:test/main.dart*''';
+    await assertStringContents(content, equals(expected));
+  }
+
   Future<void> test_forLoop_declaredVariable() async {
     final content = '''
 void f() {